On the functional anatomy of the salivary systems ofPurana tigrina Walk. (Homoptera: Cicadidae)
InPurana tigrina walk. the principal salivary system consists of several digitate lobes which are arranged in two sectors, viz. the cephalic sector and the thoracic sector, corresponding to the anterior and the posterior lobes respectively of the principal salivary gland of a generalised bug. All the lobes of both the sectors are similar in their histology and staining reactions. The accessory salivary system inP. tigrina is unique among insects. It consists of a very long convoluted, collapsible secretory tube which is more than thirty times longer and six times wider than the accessory salivary duct, the junction of the tube and the duct being indicated by a circlet of five binucleate unicellular gular glands. It is suggested that the tube serves the function of secretion and storage of watery saliva and the gular glands secrete certain material which in combination with the watery saliva, serves as stylet sheath forming material thereby favouring the penetration of the stylet fascicle into the hard bark of the stem during feeding operation. The existing fluid pressure in the tube and its collapsible nature are suggestive of the ejection of the fluid through the highly chitinous resistible duct at great force, analogous to the drilling fluid used in mechanical drilling operation.